Barring serious accidents or catastrophic mechanical failures that make repairs prohibitively expensive, when is the best time to replace your forklifts? If you’re doing routine preventative maintenance and getting small problems fixed as they crop up, then it might be difficult to tell when it makes more financial sense to stop maintaining an old machine and invest in a new one instead.

For that, you need to consider the lift’s maintenance cost per hour of its operation. A new truck that requires $1,500 of maintenance in a year and while logging 1,000 deadman hours has an operating cost of $1.50 per hour. An older truck that logs similar hours but requires $5,000 of maintenance, on the other hand, has an operating cost of $5.00 per hour—its approaching the point where it makes more sense to trade it in for a unit that costs less to operate.

With all other expenses being roughly equal among the lifts in your fleet (and if they aren’t, accounting these other differences), tracking this number for each truck is the best way to understand the real return on investment you’re getting from each forklift. A good rule of thumb is that at $5.00 or more per hour, you should think about replacing your lift, but you should crunch the numbers specific to your business to come up with the best fit for your company.